This invention relates to a method and apparatus for measuring and controlling combustion phasing in an internal combustion engine, and more particularly to an improved method and apparatus for measuring and controlling combustion phasing in a compression ignited or diesel engine based on conditions sensed in the combustion chamber using a luminosity probe and its luminosity output signal.
With modern technology and electronics, many of the operating and running conditions of an internal combustion engine can be controlled more accurately than with previous mechanical systems. For example, the control of the air/fuel ratio, spark timing, fuel injection timing and pulse width, and other adjustable factors of engine operation are greatly facilitated through the use of electronic components and electronic computers. However, in order to accurately sense the running of the engine and various phenomena occurring within the combustion chamber, it is necessary to provide a sensor that is directly positioned within the combustion chamber or in proximity to it and which senses the actual combustion conditions in the chamber.
It has been understood that knocking can be determined by an optical sensor that operates within the combustion chamber and which senses the luminosity of the gases in that chamber. A wide variety of knock detectors have been proposed that employ such sensors.
A type of engine sensor has been proposed that senses the actual luminosity of the gases within the combustion chamber. A wide variety of patents illustrating and describing the use of such sensors have issued including the following:
4,358,952; 4,369,748; 4,377,086; 4,393,687; 4,409,815; PA0 4,412,446; 4,413,509; 4,419,212; 4,422,321; 4,422,323; PA0 4,425,788; 4,468,949; 4,444,043; 4,515,132.
For the most part, these patents disclose arrangements wherein the sensor is utilized to sense only total luminosity and to equate the luminosity signal to a knocking signal.
However, the inventors have discovered that luminosity in the combustion chamber and, in particular, various gain independent parameters of the luminosity signal or curve can be used to determine the time at which various combustion conditions are occurring in the combustion chamber and can also be used to determine and control combustion phasing in an internal combustion engine, and in particular, a diesel engine. The measurements of these luminosity parameters can be incorporated into an engine control loop so as to provide the desired combustion phasing under a variety of engine operating and running conditions. In such an engine control loop, the timing or phasing of combustion can be adjusted so as to maintain a desired relationship between one or more of the gain independent luminosity parameters and output shaft or crank angle, or other timing point in the combustion cycle which corresponds to a desired combustion phasing. Alternatively, the combustion phasing can be controlled based on a predicted angle or time of occurrence of a certain combustion condition resulting from the luminosity measurement. Combustion phasing can then be adjusted so that the combustion condition occurs at the desired time in the combustion cycle, i.e., at a desired crank or output shaft angle, to attain the proper combustion phasing. These luminosity based measurements can be done on a cycle to cycle basis and individually for each cylinder of a multi-cylinder engine, and can also be done independent of variations in engine parameters such as engine speed, fuel delivery, air/fuel ratio, intake manifold pressure and temperature and injection system variations.
Control of combustion phasing can, in turn, be used to control the efficiency of the engine, fuel consumption, engine noise, peak cylinder pressure and harmful or undesirable exhaust emissions, particularly in diesel engines which emit higher quantities of exhaust smoke, particulate matter and oxides of nitrogen in comparison to spark ignited engines. Control of combustion phasing can also be used to aid engine starting.
It is, therefore, a principal object of this invention to provide an improved apparatus and method for operating an engine, and in particular a diesel engine, wherein a luminosity detector and various gain independent parameters of its luminosity signal or curve are used to control combustion phasing under a variety of engine operating and running conditions.
It is a further object of this invention to provide an improved method and apparatus for operating an engine, preferably of the diesel type, wherein various gain independent luminosity parameters are used to determine the time, which can be measured in relation to crank angle, at which certain combustion conditions are occurring in the combustion cycle, which, in turn, is used to determine and control combustion phasing under a variety of engine operating and running conditions.
It is another object of this invention to provide an improved apparatus and method for operating an engine wherein the combustion phasing of the engine can be corrected in response to various gain independent parameters of the luminosity signal so as to provide better running of the engine under a variety of engine operating and running conditions.
It is still a further object of this invention to provide an improved apparatus and method for operating an engine wherein the combustion phasing of the engine can be determined and adjusted so as to reduce cycle to cycle variations and chamber to chamber variation in multi-cylinder engine.
It is a still further object of this invention to provide engine control systems wherein the combustion phasing of the engine can be controlled in direct response to the luminosity signal, or in response to the predicted time in the combustion cycle at which certain combustion conditions occur, which is based on the luminosity signal. For example, the luminosity signal can be used to predict the output shaft or crank angle at which such combustion conditions as peak cylinder pressure, peak rate of change of pressure, start of combustion, peak rate of heat release, and 50% mass burn fraction occur. These predicted angles at which these combustion conditions occur would then provide the basis for controlling combustion phasing.
It is yet a further object of this invention to provide an improved apparatus and method for operating an engine, particularly a diesel engine, wherein the combustion phasing of the engine can be controlled so as to control or maintain NO.sub.x emissions, particulate/soot emissions, combustion related noise and fuel consumption.